Graham Platner’s announcement late Wednesday that he was suspending his Senate run in Maine plunged Democrats into a foggy, fast-paced search for a replacement — with a growing group of contenders already jostling to become the party’s new nominee.
On Thursday morning, Dr. Nirav Shah, an epidemiologist who led Maine’s response to the coronavirus pandemic and finished second in the primary for governor, became the latest Democrat to officially enter the contest, joining a fast-growing field.
In early June, Mr. Platner won the Senate nomination after more than 150,000 Democratic primary voters cast ballots for him. Now, with Mr. Platner having dropped out of the race after a rape allegation he denies, the state’s Democratic Party has been left to find a new candidate with a process it is creating on the fly.
To formally remove himself from the ballot, Mr. Platner must submit a signed request to the Maine Secretary of State’s Office by a July 13 deadline. As of Thursday morning, he had not submitted one, said Jana Spaulding, the deputy secretary of state for communications.
The party has said it will pick a new candidate through a nominating convention before a July 27 deadline set by state law. The timing and specifics of the convention had not been set as of early Thursday morning. But there was talk of allowing hundreds of Maine Democrats to vote on the nominee.
The Democrat who emerges from the process will carry the party’s hopes of unseating Senator Susan Collins, a Republican incumbent, in a race that Democrats see as key to their chances of taking back the Senate in November.
After Mr. Platner, a progressive, populist oysterman, departed the race on Wednesday, a small group of ambitious Democrats quickly moved to join the contest to replace him.
Troy Jackson, a former president of the Maine Senate favored by some progressives, said he was running. He came up short in the Democratic primary for governor in Maine last month.
“There is a powerful movement of working-class people in the state of Maine, and millions more across America who are ready to send a progressive fighter to the Senate,” Mr. Jackson, a fifth-generation logger from Allagash in northern Maine, said in a statement. He added, “I’m in.”
Hours before he entered, he secured the endorsement of Representative Ro Khanna, a California progressive who was once one of Mr. Platner’s most vocal supporters.
Jordan Wood, another progressive, also said he was entering the race. A former congressional staff member, Mr. Wood narrowly lost in the House primary in northern Maine’s swing congressional district last month.
“I’m running for U.S. Senate because to beat Susan Collins, Democrats need a candidate who can provide a true contrast and run an unapologetically progressive campaign,” he said in a text message late Wednesday. He had briefly entered the Democratic Senate primary in Maine last year before pivoting to the congressional race.
Earlier Wednesday, Dan Kleban, a founder of a brewery, said he was joining the contest, writing on Substack that Maine voters “deserve a Senator who will fight for us, not one who enables Trump at every turn.” He also had a short-lived bid for the Senate last year.
Dr. Shah, in his Thursday announcement, wrote on social media that “establishment politicians have failed us” and that “to defeat Susan Collins, we need an outsider.”
It was not immediately clear how the candidates might distinguish themselves from one another. And they might soon have more company.
Also weighin a candidacy was Shenna Bellows, the Maine secretary of state and a former state lawmaker. Like Dr. Shah and Mr. Jackson, Ms. Bellows ran for governor of Maine this year and fell short. Others may also join the contest.
The Maine Democratic Party voted Wednesday to approve the convention in a meeting with more than 100 state party members. Leaders in the state party were expected to meet again Thursday to move toward finalizing the process.
“We are going to have a nominating convention,” Charles F. Dingman, chair of the Maine Democratic Party, said Wednesday night. “And it is going to be representative.”
Another question was how involved Mr. Platner might be. On Tuesday, he received pushback from the state party, which accused him of trying to intervene in the effort to replace him before he had even exited the campaign.
“We have repeatedly reiterated to Graham Platner’s team that they have no role in determining our U.S. Senate nominee,” Devon Murphy-Anderson, the party’s executive director, said in a video on social media.
In a statement made by hand-held video that he issued on Wednesday, announcing that he was suspending his candidacy, Mr. Platner said he was “not trying to dictate to anyone” who his replacement should be. But he argued that the process should reflect “the will and the values of the people that built” his political movement.
Many of his supporters said they felt defeated by the turn in the race. “I am hugely disappointed,” said Kat Higgins, 64, a retired nurse. “I really, really liked what he said. I think everything has to change.”
Mr. Platner spent the final hours before his exit holed up with campaign advisers in his faded blue Greek Revival farmhouse in the wooded, seaside hills of Sullivan, Maine. His campaign released his video statement as the sun was setting over the Atlantic coast.
A half-dozen journalists were gathered on the street outside the home, but Mr. Platner did not emerge to address them. A single light illuminated a mudroom on the first floor.
Emily Davies and Reid J. Epstein contributed reporting.
